Igniter and gas producing device

ABSTRACT

To provide reduction in size of an igniter device and a gas generator by enhancing strength of a plug under high temperature and thereby reducing thickness of the plug, and to surely prevent electrode pins being burst forth from the plug. An igniter device comprising a resistance heating element, gunpowder to be ignited by heat generation of the resistance heating element, electrode pins connected to the resistance heating element, and a plug for holding the electrode pins, wherein material of the plug is a thermosetting resin. A gas generator comprising a cup packed with gas generant to generate gas by burning, an igniter device arranged in an interior of the cup, and a holder for holding the igniter device and the cup, wherein the holder has insertion holes for allowing the electrode pins to extend through them, respectively.

TECHNICAL FIELD

The present invention relates to an igniter device used for a gasgenerator and to a gas generator used for operating a vehicle occupantprotection system such as an automobile seatbelt pretensioner and thelike.

BACKGROUND ART

A seatbelt pretensioner and an airbag are known as a safety system toprotect a vehicle occupant from the shock in a car collision. Theseatbelt pretensioner and the like are brought into action by a largeamount of gas introduced from the gas generator, for the protection ofthe vehicle occupant. The gas generator includes an igniter device andgas generant and is structured so that when a car collision happens, theigniter device is brought into action to ignite and burn the gasgenerant, so as to generate the large amount of gas rapidly.

An example of the conventional igniter device used for the gas generatoris shown in FIG. 5, which is an igniter device 104 having a plug 107formed of thermoplastic resin and the like and fitted in a cup 112 toseal an enhancer agent 103 in the cup 112. The plug 107 is provided withtwo electrode pins 108, 109 extending through it. The electrode pins108, 109 are projected into an interior of the cup 112 and electricallyconnected with an electric bridge-circuit wire 110 at tip ends thereof.The electric bridge-circuit wire 110 is covered with a firing agent 111contacting with the enhancer agent 103. The firing agent 111 has goodignition sensitivity so that it can be ignited by the heating of theelectric bridge-circuit wire 110 to ignite the enhancer agent 103.

The igniter device 104 is mounted to the gas generator, to allow anelectric current to flow through it in accordance with collision signalsfrom collision sensors, so as to heat the electric bridge-circuit wire110. The electric bridge-circuit wire 110 heated ignites the firingagent 111 and in turn ignites and burns the enhancer agent 103. Then,the pressure and heat generated by the burning of the enhancer agent 103causes the ignition and burning of the gas generant 101 and, then, thegas generated is spurted into the seatbelt pretensioner.

Also, an example of the conventional gas generator for the seatbeltpretensioner is shown in FIG. 6. The gas generator 100 of FIG. 6comprises the gas generant 101 that generates a large amount of gas whenignited, an igniter device 104 (Cf. FIG. 5) containing an enhancer agent103 which is ignited by the passage of electric current through theigniter device, a cup 102 containing the gas generant 101, an ignitercase 114 to cover the cup 112, a holder 106 to hold the igniter device104 and the igniter case 114 concentrically and seal the gas generant101 and the igniter device 104 in an inner space between the holder 106and the cup 102, an O-ring 115 disposed in a gap between the igniterdevice 104 and the holder 106 to prevent infiltration of moisture fromthe gap therebetween, and a shorting clip 113 to keep two electrode pins108, 109 standing from the igniter device 104 in a shorted state. Also,a sealant, not shown, is applied to the gap between the cup 102 and theholder 106, to prevent moisture infiltrating into the gap therebetween.

It is should be noted here that the plug 107 is formed of thermoplasticresin. Specifically, synthetic resin, such as polybutylene terephthalate(PBT), nylon 6, and nylon 66, in which glass fibers and the like aremixed, is used for the plug 107 (Cf. Patent Document 1, for example).

It is also proposed that thermosetting resin of unsaturated polyesterresin and the like is used for the plug (Cf. Patent Document 2, forexample).

Patent Document 3 discloses a gas generator including an igniter devicehaving a plug comprising an insulating supporting portion formed ofepoxy resin, a cylindrical metal sleeve, and a molded sheath portionformed of thermoplastic resin.

Patent Document 4 discloses an igniter device which has a plugcomprising a solid body and a glass sheath and is sealed by epoxy resin.

Patent Document 5 discloses a gas generator including an igniter devicehaving a header (plug) formed of thermoplastic resin or thermosettingresin of unsaturated polyester.

Patent Document 6 discloses a gas generator including an igniter devicehaving a header (plug) formed of glass-fiber-reinforced resin.

Further, Patent Document 7 discloses a gas generator having a holderwith two insertion holes for allowing two electrode pins to pass throughrespectively and an igniter device having a hermetic membercorresponding to a plug formed of insulating resin.

Patent Document 1: JP Publication (Publication No. 2003-25950) of JPUnexamined Patent Application (Page 4 and FIG. 4);

Patent Document 2: JP Publication (Publication No. 2002-90097) of JPUnexamined Patent Application (Page 5);

Patent Document 3: JP Publication (Publication No. 2000-108838) of JPUnexamined Patent Application (Page 5);

Patent Document 4: JP Publication (Publication No. 2000-241099) of JPUnexamined Patent Application (Pages 4 and 5);

Patent Document 5: Pamphlet of International Publication (PublicationNo. WO01/031281);

Patent Document 6: Pamphlet of International Publication (PublicationNo. WO01/031282); and

Patent Document 7: JP Publication (Publication No. 2000-292100) of JPUnexamined Patent Application (FIG. 1).

DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

It is common in the conventional ignition device that the resin plugused for sealing the enhancer agent in the cup is formed ofthermoplastic resin, as previously mentioned. The plug formed ofthermoplastic resin has the possible problem that when the igniterdevice is incorporated in the gas generator for intended use and the gasgenerant is fired and burnt in the vehicle fire at the car collision orin the trial burn of the gas generator in an unexpected high-temperaturestate, the plug formed of thermoplastic resin may be softened so thatthe two electrode pins extending through the plug may be burst forth bythe pressure of high-pressure gas in the gas generator. When the plug isincreased in thickness, in order to prevent this possible situation, theigniter device is increased in size to that extent, so that the gasgenerator is increased in size or an amount of gas generant packed inthe gas generator is reduced if the size of the gas generator cannot beincreased any further. Further, in the case where the plug is producedto have the electrode pins and electrode-pin inserting portions whichare formed of metal and sealed with glass, the parts cost comes high andthe glass melting process is required for manufacturing the plug. As aresult, the manufacturing cost comes high and resultantly the plug comesexpensive.

On the other hand, the plug formed of unsaturated polyester compositionhas the disadvantage of poorness in productivity, because a relativelylong time is required for curing the unsaturated polyester compositioncompletely. It also has the disadvantage that when peroxide is used as acure reaction initiator, the composition is dissolved easily due to theunstableness of peroxide, causing deterioration in workability.

Also, the plug formed by a plurality of components has the problem withthe sealing properties between the components. It also involves thedisadvantage that the parts count is increased, involving time-consumingworks in manufacturing.

It is an object of the present invention to reduce the size of theigniter device by enhancing the strength of the plug under hightemperature and thereby reducing thickness of the plug, without anysignificant reduction in productivity; to surely prevent the electrodepins being burst forth from the plug; to provide the igniter device thatcan ensure the sealing properties between the plug and the electrodepins; and to provide a gas generator using the same igniter device. Itis another object of the present invention to produce the gas generatorcomprising the electrode pins and the holder which are integrally moldedusing thermosetting resin, or preferably epoxy resin.

MEANS FOR SOLVING THE PROBLEM

The present invention provides an igniter device comprising a resistanceheating element, gunpowder to be ignited by heat generation of theresistance heating element, electrode pins connected to the resistanceheating element, and a plug for holding the electrode pins, whereinmaterial of the plug is a thermosetting resin.

The igniter device of the present invention may be constructed so thatit comprises a cup containing an enhancer agent, a plug, fitted in thecup, to seal the enhancer agent packed in the cup, two electrodesextending through the plug, an electric bridge-circuit wireinterconnecting ends of the two electrode pins located in the cup, and afiring agent covering the electric bridge-circuit wire and contactingwith the enhancer agent, and the plug is formed of a thermosettingresin.

It is preferable in the igniter device of the present invention that theepoxy resin composition comprises an epoxy resin and a curing agent.Preferably, the epoxy resin composition contains 30-95 weight % fillerof the total epoxy resin composition. It is preferably that the fillercomprises at least one of molten silica, crystallized silica, aluminumoxide, and calcium carbonate. It is preferable that the epoxy resincomprises at least one of bisphenol type epoxy resin, novolak type epoxyresin, biphenyl type epoxy resin, naphthalene type epoxy resin,alicyclic epoxy resin, and amines epoxy resin. It is preferable that thecuring agent comprises at least one of phenol novolak resin, acidanhydride, and amines. Preferably, the epoxy resin composition comprisesa curing accelerator. It is preferable that the plug has, at a portionthereof on the holder side, a stepped portion which is formed so thatthe portion thereof on the holder side is reduced in diameter.

Also, the present invention provides a gas generator comprising a cuppacked with gas generant to generate gas by burning, an igniter devicearranged in an interior of the cup, and a holder for holding the igniterdevice and the cup, the igniter device comprising a resistance heatingelement, gunpowder to be ignited by heat generation of the resistanceheating element, electrode pins connected to the resistance heatingelement, and a plug for holding the electrode pins, wherein material ofthe plug is a thermosetting resin, and wherein the holder has insertionholes for allowing the electrode pins to extend through them,respectively.

The gas generator of the present invention may have the igniter deviceof the present invention. The gas generator of the present invention maybe constructed so that it comprises a second cup packed with gasgenerant to generate gas by burning, an igniter device arranged in aninterior of the second cup and having a first cup containing an enhanceragent, and a holder for holding the igniter device and the second cup,the igniter device comprising a plug, fitted in the first cup, forsealing the enhancer agent in the first cup, and two electrode pinsextending through the plug toward the holder, wherein the holder has twoinsertion holes for allowing the two electrode pins to extend throughthem, respectively, and wherein the plug is formed of thermosettingresin composition.

It is preferable that root portions of the electrode pins extending fromthe plug are sheathed with skirt portions formed to be integral with theplug and the skirt portions are inserted in the insertion holes. It ispreferable that the plug has, at a portion thereof on the holder side, astepped portion which is formed so that the portion thereof on theholder side is reduced in diameter. Preferably, the plug is formed ofepoxy resin composition. It is preferable that a cross-section area ofthe two insertion holes is more than once to ten times or less across-section area of the electrode pins. Also, it is preferable that asealing material for sealing a space between the holder and the plug isarranged near the stepped portion.

EFFECT OF THE INVENTION

According to the igniter device of the present invention, since the plugis formed of thermosetting resin, the plug has a sufficient strengthunder high temperature and is resistant to softening in the hightemperature state, thus enabling the electrode pins to be prevented frombeing dropped out from the plug. This can ensure the strength requiredfor preventing the electrode pins from being burst forth even when theplug is reduced in thickness, thus allowing reduction in size of theigniter device to the extent corresponding to the reduction in thicknessof the plug.

In the gas generator of the present invention, the two electrode pinsare inserted in the two small insertion holes formed in the holder,respectively. Due to this, even when the enhancer agent is burnt to putthe second cup in a high-temperature and high-pressure state, since agreater part of the end face of the plug is abutted with and surelyreceived by the holder, the two electrode pins are resistant to beingburst forth from the holder. In addition, since the electrode pins areinserted in the insertion holes to be closely spaced from the holder,when static electricity flows in the electric test, the staticelectricity is discharged and escaped from the space between part of theelectrode pins around which neither the gunpowder nor the enhancer agentis arranged and the holder, to prevent the electric discharge that maycause the firing of the gunpowder and the enhance.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, an igniter device 4 of the present inventioncomprises an enhancer agent 10, a first cup 11 for covering andcontaining the enhancer agent 10, a plug 13, partly fitted in the firstcup 11, for sealing the enhancer agent 10 in the first cup 11, and twoelectrode pins 14, 15 extending through the plug 13 toward a holder 5.As shown in FIG. 1, the two electrode pins 14, 15 are electricallyconnected with each other at tip ends thereof on the first cup 11 sidethrough a resistance heating element 16, and the resistance heatingelement 16 is covered with a firing agent 17 contacting with theenhancer agent 10. In short, the igniter device 4 is structured so thatwhen electric current flows through the electrode pins 14, 15, theresistance heating element 16 can be heated to cause ignition of thefiring agent 17 and in turn cause ignition and burning of the enhanceragent 10 which is in contact with the firing agent 17. In the ignitiondevice 4 of the present invention, it is preferable that the use of theenhancer agent 10 is eliminated. In this variant, an amount of gunpowderof the firing agent 10 covering the resistance heating element 16 isadjusted so that the substantially same effect as the effect theignition device with the enhancer agent 10 produces can be produced. Itis further preferable in this variant that the first cup is eliminated.The method of covering the enhancer agent for storage is notparticularly limited to the use of the cup. As an alternative to thecup, coating resin over the enhancer agent may be used, for example.

It is preferable that the materials used for the electrode pins 14, 15include, iron, stainless steel, and alloys containing nickel. Theresistance heating element 16 includes the so-called electricbridge-circuit wire formed of metal such as, for example,nickel-chromium alloy, and platinum. The heaters (SCB) using thesemiconductor manufacturing techniques are preferably used as theresistance heating element 16. Among others, the one using a reactivebridge is further preferably used as the resistance heating element.

The first cup 11 has a closed-end cylindrical shape, having a flameleading portion 11 a formed in the bottom for leading the heat currentgenerated when the enhancer agent 10 in the first cup 11 is ignited tothe gas generant 2 in the second cup 3 (FIG. 2). The flame leadingportion 11 a may have a notch which is called a score. Further, thefirst cup 11 has an engaging portion 11 b which is formed at an endportion thereof on the opening side, to be engaged with the plug 13. Thematerials that may be used for forming the first cup 11 include, forexample, plastic materials, such as polybutylene terephthalate,polyethylene terephthalate, NYLON 6, and NYLON 66.

In the igniter device 4 of the present invention, when a specifiedelectric current flows between the electrode pins 14, 15, the resistanceheating element 16 generates heat instantaneously. This heat generationallows the stable ignition of the firing agent and in turn allows theburning of the enhancer agent 10. As a result, an internal pressure ofthe first cup 11 rises, so that the bottom (the flame leading portion 11a) of the first cup 11 is burst. Then, the flame of the enhancer agent10 spurts from the igniter device into the gas generator.

The igniter device 4 of the present invention is usually produced takingthe following steps: (1) the step of forming two electrode pins, (2) thestep of forming the plug 13, (3) the step of forming welding surfaces onthe electrode pins 14, 15, respectively, (4) the step of welding theresistance heating element 16 thereon, (5) the step of coating theresistance heating element 16 with the firing agent, (6) the step ofcontacting the firing agent with the enhancer agent 10, and (7) the stepof fitting the plug 13 into the first cup 11.

The gas generator using the igniter device 4 of the present invention isshown in FIG. 2. In this gas generator 1, the first cup 11 of theigniter device 4 is wholly covered by a closed-end igniter case (whichis also called a squib case) 12 (FIG. 2). The igniter case 12 has aflame leading portion 12 a, formed in the bottom, for leading the heatcurrent to the gas generant 2 in the second cup 3. It also has a taperedflange portion 12 b, formed at an end thereof on the opening side, formounting the igniter case on the holder 5. This squib case 12 can beformed of metal, such as, for example, iron, stainless steel, andaluminum, or synthetic resin, such as, for example, PBT (polybutyleneterephthalate), and fluorocarbon resin. The first cup 11 containing theenhancer agent 10 is sheathed by the igniter case 12, so that the firstcup 11 is held with an increased force to prevent from being burstbefore the internal pressure of the first cup 11 rises to apredetermined value when the enhancer agent 10 is ignited. Hence, theenhancer agent 10 can be burnt under a high pressure. As a result, aburning rate of the enhancer agent 10 is increased, so that an ignitiondelay of the gas generant 2 is decreased. The flame leading portion 11 aof the first cup 11 and the flame leading portion 12 a of the ignitercase 12 are not necessarily formed in the bottoms thereof.Alternatively, one or more flame leading portions 11 a and 12 a may beformed in a circumferential side wall of the first cup 11 and in acircumferential side wall of the igniter case 12, respectively.

As shown in FIG. 1, the plug 13 includes an inserting portion 13 ainserted with an internal fit in the first cup 11, a large diameterportion 13 b enlarged radially from a base end of the inserting portion13 a in a tapered form, and a small diameter portion 13 c having adiameter smaller than that of the large diameter portion and extendingcontinuously to the large diameter portion 13 b through a steppedportion 13 e. An intermediate portion 13 f extending from the largediameter portion 13 b to the small diameter portion 13 c is in the formof a plane perpendicular to the extending-in-parallel portions of theelectrode pins 14, 15. Thus, the plug 13 is configured so that the largediameter portion 13 b can be reduced in thickness by forming the steppedportion 13 e at a left end portion thereof (an end thereof on the holder5 side). The inserting portion 13 a of the plug 13 is inserted with theinternal fit within the first cup 11 and engaged with the engagingportion 11 b to prevent the plug 13 from dropping out of the first cup11. Preferably, the plug 13 b has thickness in the range of 1.6 mm-2 mm.

As shown in FIG. 2, a gasket 18 (sealing material) to preventinfiltration of moisture into the second cup 3 from between the plug 13and the holder 5 is arranged at a location adjacent to the steppedportion 13 e on the left side of the large diameter portion 13 b.Instead of the gasket 18, a sealing agent in liquid form may be appliedto therebetween. Further, the igniter case 12 and the plug 13 are fixedto the holder 5 by crimping an annular lug 5 c of the holder 5 in thestate of the tapered flange portion 12 b of the igniter case 12 being inclose contact with the tapered surface of the large diameter portion 13b.

The two electrode pins 14, 15 extend through the plug 13 so that one endportions thereof project into the first cup 11 and the other endportions thereof extending toward the holder 5 extend through the holder5. The end portions of the electrode pins 14, 15 projecting into thefirst cup 11 are electrically connected with each other via theresistance heating element 16. On the other hand, root portions of theelectrode pins projecting from the plug 13 toward the holder 5 aresheathed with the truncated-cone-shaped skirt portions 13 d projectingslightly from the small diameter portion 13 c of the plug 13 toward theholder 5.

In general, thermosetting resin is used as the material of the plug 13.Of the thermosetting resins, epoxy resin composition is preferably usedfor the plug 13 in terms of the thermosetting property and the moistureresistance. Preferably, the thermosetting resin composition comprises anepoxy resin and a curing agent. It is to be noted that althoughunsaturated polyester is a thermosetting resin having substantially thesame fire resistance property as the epoxy resin composition, since itis inferior to the epoxy resin composition in adhesiveness to metal, itis not of preferable.

The epoxy resins that may be used for the plug include, for example,polyfunctional epoxy resins which are glycidyl-etherified polyphenolscompounds, polyfunctional epoxy resins which are various types ofglycidyl-etherified novolak resins, alicyclic epoxy resins, aliphaticepoxy resins, heterocyclic epoxy resins, glycidyl esters epoxy resins,glycidyl amines epoxy resins, and epoxy resins obtained by the reactionof halogenated phenols with glycidyl.

The polyfunctional epoxy resins which are glycidyl-etherifiedpolyphenols compounds include, for example, phenol, cresol, bisphenol A,bisphenol F. bisphenol S, 4,4′-biphenyl phenol, tetramethyl bisphenol A,dimethyl bisphenol A, tetramethyl bisphenol F, dimethyl bisphenol F.tetramethyl bisphenol S, dimethyl bisphenol S,tetramethyl-4,4′-biphenol, dimethyl-4,4′-biphenylphenol,1-(4-hydroxydiphenyl)-2-[4-(1,1-bis-(4-hydroxydiphenyl)ethyl)phenyl]propane,2,2′-methylene-bis(4-methyl-6-tert-butylphenol),4,4′-butylidene-bis(3-methyl-6-tert-butylphenol),trishydroxyphenylmethane, resorcinol, hydroquinone, pyrogallol, phenolshaving a dulsopropylidene skeleton, phenols having a fluorene skeleton,such as 1,1-di-4-hydroxyphenylfluorene, and epoxy resins which areglycidyl-etherified polyphenol compounds, such as phenolizedpolybutadiene.

The polyfunctional epoxy resins which are various types ofglycidyl-etherified novolak resins include, for example, novolak resinsusing as raw materials various types of phenols, such as phenol,cresols, ethyl phenols, butyl phenols, octyl phenols, bisphenol A,bisphenol F, bisphenol S, and naphthols, phenol novolak resin having axylylene skeleton, phenol novolak resin having a dicyclopentadieneskeleton, phenol novolak resin having a biphenyl skeleton, and phenolnovolak resin having a fluorene skeleton.

The alicyclic epoxy resins include those having a cyclohexane skeleton,such as, for example,3,4-epoxycyclohexylmethyl-3′,4′-cyclohexylcarboxylate.

The aliphatic epoxy resins include, for example, glycidyl ethers ofpolyhydric alcohol, such as 1,4-butamediol, 1,6-hexanediol, polyethyleneglycol, polypropylene glycol, and pentaerythritol, xylene glycolderivative.

The heterocyclic epoxy resins include, for example, those having aheterocyclic ring, such as an isocyanuric ring and a hydantoic ring.

The glycidyl esters epoxy resins include, for example, epoxy resinscomprising carboxylic acids, such as diglycidyl ester hexahydrophthalateand diglycidyl ester tetrahydlrophthalate.

The glycidyl amines epoxy resins include, for example, epoxy resinsobtained by the reaction of amines with glycidyl, such as aniline,toluidine, p-phenylenediamine, m-phenylenediamine,diaminodiphenylmethane derivative, and diaminomethylbenzene derivative.

The epoxy resins obtained by the reaction of halogenated phenols withglycidyl include, for example, those, such as bromized bisphenol A,bromized bisphenol F, bromized bisphenol S, bromized phenol novolak,bromized cresol novolak, chloridized bisphenol S, chloridized bisphenolA, and bromophenol.

No particular limitation is imposed on the use of those epoxy resins.Those epoxy resins may be properly selected in accordance with intendedpurposes and applications. Preferably, bisphenol type epoxy resin,novolak type epoxy resin, biphenyl type epoxy resin, naphthalene typeepoxy resin, alicyclic epoxy resin, and amines epoxy resin are used.Bisphenol A type epoxy resin and novolak type epoxy resin areparticularly preferable. Further, these epoxy resins may be selectedaccording to the need of e.g. electric insulation, adhesion,water-resistance, dynamical strength, and workability and may be used inthe form of a mixture of one or two or more materials.

The curing agents include, for example, acid anhydride, amines, phenols,and imidazoles.

The acid anhydrides include, for example, aromatic carboxylic anhydride,such as phthalic anhydride, trimellitic anhydride, pyromelliticanhydride, benzophenone tetracarboxylic anhydride, ethylene glycolanhydrous trimellitic acid, and biphenyl tetracarboxylic anhydride,aliphatic carboxylic anhydride, such as azelaic acid, sebacic acid, anddodecandioic acid, and alicyclic carboxylic anhydride, such astetrahydrophthalic anhydride, hexahydrophthalic anhydride, nadicanhydride, chlorendic anhydride, and himic anhydride. The phthalicanhydrides include, for example, 4-methylhexahydrophthalic anhydride.The 4-methylhexahydrophthalic anhydride is particularly preferable.

The amines include, for example, aromatic amines, such asdiaminodiphenylmethane, diaminodiphenylsulfone, anddiaminodiphenylether, aliphatic amines, and modified amines.

The phenols include, for example, bisphenol A, tetrabrombisphenol A,bisphenol F, bisphenol S, 4,4′-biphenyl phenol,2,2′-methylene-bis(4-methyl-6-tert-butylphenol),2,2′-methylene-bis(4-ethyl-6-tert-butylphenol),4,4′-butylidene-bis(3-methyl-6-tert-butylphenol),1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenol,trishydroxyphenylmethane, pyrogallol, phenols having a dulsopropylideneskeleton, phenols having a fluorene skeleton such as1,1-di-4-hydroxyphenylfluorene, polyphenol compounds, such as phenolizedpolybutadiene, novolak resins using as raw materials various types ofphenols such as phenol, cresols, ethyl phenols, butyl phenols, octylphenols, bisphenol A, bromized bisphenol A, bisphenol F, bisphenol S,and naphthols, and various types of novolak resins, such as a phenolnovolak resin having a xylylene skeleton, a phenol novolak resin havinga dicyclopentadiene skeleton, and a phenol novolak resin having afluorene skeleton.

The imidazoles include, for example, various types of imidazoles, suchas 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole,2-heptadecylimidazole, 2-phenyl-4-methylimidazole,1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole,1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole,1-cyanoethyl-2-undecylimidazole,2,4-diamino-6(2′-methylimidazole(1′))ethyl-s-triazine,2,4-diamino-6-(2′-undecylimidazole(1′))ethyl-s-triazine,2,4-diamino-6-(2′-ethyl-4-methylimidazole(1′))ethyl-s-triazine, anadduct of2,4-diamino-6-(2′-methylimidazole(1′))ethyl-s-triazine-isocyanuric acid,a 2:3 adduct of 2-methylimidazole isocyanuric acid, an adduct of2-phenylimidazole isocyanuric acid,2-phenyl-3,5-dihydroxymethylimidazole,2-phenyl-4-hydroxymethyl-5-methylimidazole, and1-cyanoethyl-2-phenyl-3,5-dicyanoethoxymethyl imidazole, and saltscomprising the imidazoles and polyvalent carboxylic acid such asphthalic acid, isophthalic acid, telephthalic acid, trimellitic acid,pyromellitic acid, naphthalenedicarboxylic acid, maleic acid, and oxalicacid. These curing agents are suitably selected according to therequired property for the ignition squib structure or the requiredworkability. Preferably, the curing agents are selected from the groupconsisting of the acid anhydrides, the phenol novolak resins, and theamines. The amount of curing agent used is determined so that anequivalent ratio of the curing agent to the thermosetting resin can fallin the range of from 0.3 to 2.0, preferably from 0.4 to 1.6, or furtherpreferably from 0.5 to 1.3. Two or more curing agents may be mixed foruse. Also, the imidazols may be used as a curing accelerator.

The curing accelerators include, for example, various types ofimidazoles, such as 2-methylimidazole, 2-phenylimidazole,2-undecylimidazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole,1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole,1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole,1-cyanoethyl-2-undecylimidazole,2,4-diamino-6(2′-methylimidazole(1′))ethyl-s-triazine,2,4-diamino-6-(2′-undecylimidazole(1′))ethyl-s-triazine,2,4-diamino-6-(2′-ethyl-4-methylimidazole(1′))ethyl-s-triazine, anadduct of 2,4-diamino-6-(2′-methylimidazole(1′))ethyl-s-triazineisocyanuric acid, a 2:3 adduct of 2-methylimidazole isocyanuric acid, anadduct of 2-phenylimidazole isocyanuric acid,2-phenyl-3,5-dihydroxymethylimidazole,2-phenyl-4-hydroxymethyl-5-methylimidazole, and1-cyanoethyl-2-phenyl-3,5-dicyanoethoxymethyl imidazole, saltscomprising the imidazoles and polyvalent carboxylic acid, such asphthalic acid, isophthalic acid, telephthalic acid, trimellitic acid,pyromellitic acid, naphthalenedicarboxylic acid, maleic acid, and oxalicacid, salts comprising amides such as dicyandiamide, diaza compounds,such as 1,8-diaza-bicyclo(5,4,0)undecene-7, and their phenols, thepolyvalent carboxylic acids, or phosphinic acids, ammonium salts, suchas tetrabutyl ammonium bromide, cetyltrimethyl ammonium bromide, andtrioctylmethyl ammonium bromide, phosphinic acids, such astrioctylphosphine and tetraphenylphosphonium tetraphenylborate, phenols,such as 2,4,6-triaminomethylphenol, amine adducts, and microencapsulatedcuring accelerators in which those curing agents are encapsulated. Thesecuring accelerators are suitably selected according to the requiredproperties for the transparent resin composition, such as transparency,a curing rate, and working conditions. The amount of curing acceleratorused is determined so that a ratio of the curing accelerator to thethermosetting resin can fall in the range of 0.1-5 parts by mass, orpreferably in the order of 1 part by mass, per 100 parts by mass of thethermosetting resin.

The fillers include, for example, various types of silica, such as fumedsilica, and crystallized silica, silicon carbide, silicone nitride,boron nitride, calcium carbonate, magnesium carbonate, barium sulfate,calcium sulfate, mica, talc, clay, aluminum oxide, magnesium oxide,zirconium oxide, aluminum hydroxide, magnesium hydroxide, calciumsilicate, aluminum silicate, lithium aluminum silicate, zirconiumsilicate, barium titanate, glass fiber, carbon fiber, molybdenumdisulfide, and asbestos. Preferably used are fumed silica, crystallizedsilica, calcium carbonate, aluminum oxide, aluminum hydroxide, andcalcium silicate. Further preferably used are molten silica,crystallized silica, aluminum oxide, and calcium carbonate. Thesefillers are suitably selected according to the required performance andworkability and the amount of filler used is determined so that a ratioof the filler to the total amount of thermosetting resin composition canfall in the range of 30-95 weight %, preferably 40-90 weight %, orfurther preferably 50-90 weight %. These fillers may be used singly orin combination of two or more.

Also, a colorant, a coupling agent, a leveling agent, and a lubricant,may be added to the epoxy resin composition for intended purposes.

No particularly limitation is imposed on the colorant. The colorantsinclude, for example, various types of organic coloring matters, such asphthalocyanine, azo, disazo, quinacridone, anthraquinone, flavanthrone,perinon, periren, dioxazine, condensed azo, and azomethine, and varioustypes of inorganic coloring matters, such as titanium oxide, leadsulfate, chrome yellow, zinc yellow, chrome, vermillion, colcothar,cobalt violet, iron blue, ultramarine blue, carbon black, chrome green,chromic oxide green, and cobalt green.

The coupling agents include, for example, silane coupling agents, suchas 3-glycidoxypropyltrimethoxy silane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxy silane,2-(3,4-epoxycyclohexyl)ethyltrimethoxy silane,N-(2-aminoethyl)3-aminopropylmethyldimethoxy silane,N-(2-aminoethyl)3-aminopropylmethyltrimethoxy silane,3-aminopropyltriethoxy silane, 3-mercaptopropyltrimethoxy silane,vinyltrimethoxy silane,N-(2-vinylbenzylamino)ethyl)3-aminopropyltrimethoxy silanehydrochloride, 3-methacryloxypropyltrimethoxy silane,3-chloropropylmethyldimethoxy silane, and 3-chloropropyltrimethoxysilane, titanium coupling agents, such asisopropyl(N-ethylaminoethylamino)titanate, isopropyltriisostearoyltitanate, titaniumdi(dioctylpyrophosphate)oxyacetate,tetraisopropyldi(dioctylphosphite)titanate, andneoalkoxytri(p-N-(β-aminoeethyl)aminophenyl)titanate, and zirconium oraluminum coupling agents, such as Zr-acetylacetonate, Zr-methacrylate,Zr-propionate, neoalkoxy zirconate, neoalkoxytrisneodecanoyl zirconate,neoalkoxytris(dodecanoyl)benzenesulfonyl zirconate,neoalkoxytris(ethylenediaminoethyl)zirconate,neoalkoxytris(m-aminophenyl)zirconate, ammonium zirconium carbonate,Al-acetylacetonate, Al-methacrylate, and Al-propionate. Preferably usedis the silicon coupling agent. The use of the coupling agent can providehardened material of excellent reliability in moisture resistance andless reduction in adhesion strength after moisture absorbent.

The leveling agents include, for example, oligomers of the molecularweight in the range of 4,000-12,000 comprising acrylates, such as ethylacrylate, butyl acrylate, and 2-ethylhexyl acrylate, epoxidated soybeanfatty acid, epoxidated abiethyl alcohol, hydrogenerated ricinus, andtitanic coupling agent.

The lubricants include, for example, hydrocarbon lubricants, such asparaffin wax, micro wax, and polyethylene wax, lubricants of higherfatty acid, such as lauric acid, myristic acid, palmitic acid, stearicacid, arachic acid, and behenic acid, lubricants of higher fatty acidamide, such as stearyl amide, palmithyl amide, oleyl amide,methylenebisstearo amide, and ethylenebisstearo amide, lubricants ofhigher fatty acid ester, such as hardened ricinus, butyl stearate,ethylene glycol monostearate, and pentaerythritol(mono-, di-, tri-, ortetra-)strearate, lubricants of alcohols, such as cetyl alcohol, stearylalcohol, polyethylene glycol, and polyglycerol, metallic soaps ofmetallic salts, such as magnesium, calcium, cadmium, barium, zinc, andlead of lauric acid, myristic acid, palmitic acid, stearic acid, arachicacid, behenic acid, recinoleic acid, and naphthenic acid, and naturalwaxes, such as carnuba wax, candelilla wax, yellow beeswax, and montanwax.

The epoxy resin composition is prepared in the following manner. Whenthe components blended, such as the epoxy resin and the curing agent,and, if required, the curing accelerator, the filler, the colorant, thecoupling agent, the leveling agent, and the lubricant, are in solidform, the components blended are mixed using a mixer, such as a Henschelmixer or a Nauter mixer, and, then, the mixture is kneaded at 80-120° C.using a kneader, an extruder, and a heating roller. After cooled, theresultant mixture is pulverized to powders, to thereby produce thethermosetting resin composition. On the other hand, the componentsblended are in liquid form, they are mixed to be dispersed uniformlyusing a planetary mixer and the like, to thereby produce thethermosetting resin composition. If the viscosity of the liquidcomposition obtained is so high that the workability is deteriorated,then it may be adjusted to an adequate viscosity for the work by addinga solvent thereto. Also, the solid composition may be converted to aliquid form. In this case, the solid thermosetting resin compositionobtained in the manner mentioned above may be dissolved in the solventto prepare the liquid composition, or alternatively, the components tobe blended may be dissolved in the solvent to prepare the liquidcomposition. Any particular limitation is imposed on the solvent used.As long as it is usually used as the solvent, any solvent may be usedfor preparation of the liquid composition. In the case where thethermosetting resin composition thus obtained is in solid form, it iscommon that after pelletized and then molded in a low pressure transfermolding machine, it is heated to 100-200° C. to be cured. On the otherhand, in the case where the thermosetting resin composition is in liquidform, it is common that after subjected to a cast molding or dispensed,it is heated to 100-200° C. to be cured.

In this connection, the epoxy resin mentioned above has a high glasstransition point and a high strength under high temperature.Particularly preferably, the epoxy resin composition has a glasstransition temperature higher than an autogenous ignition temperature ofthe gas generator. Further preferably, the epoxy resin composition has ahigher glass transition temperature (e.g. 180° C. or more) than anautogenous ignition temperature of the gas generant packed in the gasgenerator. By forming the plug 13 of this epoxy resin composition, therecan be provided the following results: Even when the enhancer agent 10is ignited to put the first cup 11 in a high-temperature andhigh-pressure state, the plug 13 can be prevented from being softened,thus making it hard for the electrode pins 14, 15 to be burst forth fromthe plug 13. Also, even when the plug 13 is reduced in thickness, thestrength of the plug at the high temperature can be fully ensured. Thiscan allow size reduction of the gas generator 1 to that extent or volumeincrease of the second cup 3, without changing the size, and as such canallow an increased amount of gas generant 2 packed. Hence, even when thegas generant (green propellants) which does not contain the smokelessgunpowder mentioned above, for which an increased amount of powderpacked is required due to its less gas-generation efficiency, andproduces a small amount of harmful gas components is used, the gasgenerator 1 need not be increased in size. Further, since the epoxyresin composition has good adhesiveness to the metal, the igniter device4 of the present invention is improved in adhesion between the plug 13and the electrode pins 14, 15, thus eliminating the need of using thesealing member for sealing the space therebetween. Also, when the holder5 is formed of metal and is molded to be integral with the plug 13, theholder 5 can protect the first cup 11 containing the enhancer agent 10against moisture infiltrating into the first cup 11 as much as possiblewithout using the sealing member between the holder 5 and the plug 13.

In FIG. 2, a shorting clip 19 to keep the two electrode pins 14, 15 ashorted state is fixed in the gas generator 1 using the igniter device 4of the present invention. This shorting clip 19 serves to preventoperational error of the igniter deice 4 that may be caused by staticelectricity and the like.

In the gas generator 1 using the igniter device 4 of the presentinvention, the holder 5 for holding the igniter device 4 has projections5 a formed around its outer circumference. The projections 5 a arecrimped onto a flange portion 3 d of the second cup 3 to fix the secondcup 3 to the holder 5. Also, the holder 5 has a concave, plugaccommodating portion 5 b formed at a portion thereof on the right sideand an annular projection 5 c projecting from a circumferential end ofthe accommodating portion 5 b to the right side. The igniter case 12 andthe plug 13 are fixed to the holder 5 by crimping, so that the annularprojection 5 c is put in abutment with the tapered flange portion 12 bof the igniter case 12 in the state of the plug 13 being partlyaccommodated in the accommodating portion 5 b.

As previously mentioned, the plug 13 is formed to have the steppedportion 13 e, and the corresponding accommodating portion 5 b of theholder 5 to provide accommodation for the plug 13 comprises alarge-diameter accommodating opening 21 for providing accommodation forthe large diameter portion 13 b of the plug 13 and a small-diameteraccommodating opening 22 of the plug 13, extending continuously with thelarge-diameter accommodating hole 21, for providing accommodation forthe small diameter portion 13 c of the plug 13. Since the large diameterportion 13 b of the plug 13 is reduced in thickness by forming thestepped portion 13 e in the plug 13, an engaging portion of the holder 5to be engaged with the large diameter portion 13 b of the plug 13 can bemade larger in thickness than an engaging portion of the holder 5 to beengaged with the small diameter portion 13 c of the same. This canensure that the strength of the holder 5 is kept in the high pressurestate when the gas generant 2 is burnt at the high temperature.

It is preferable for the igniter device of the present invention thatsupporting members for sheathing the electrode pins are not included inthe plug. In other words, the plug is molded into one piece from theepoxy resin. This can provide reduced number of components of the plug,as compared with the plug formed by a plurality of components includingthe supporting members. This can expect to provide reduced costs of theigniter device.

The present invention can provide a compact gas generator suitably usedfor a seatbelt pretensioner for an automotive vehicle by using theigniter device. Description on the gas generator of the presentinvention will be given. The gas generator 1 shown in FIG. 2 comprisesthe second cup member 3 packed with the gas generant 2 to generate gasby the burning, the igniter device 4 having the first cup 11, arrangedin the interior of the second cup 3, for containing the enhancer agent10, the igniter case 12 having the flame leading holes 12 a covering thefirst cup, and the holder 5 for holding the igniter case 12 and thefirst cup 11 by crimping the annular projection 5 c onto the holder 5.

As shown in FIGS. 2 and 4, the holder 5 has two insertion holes 23, 24 5formed to extend parallel downwardly from a bottom end of theaccommodating opening 22. The portions of the two electrode pins 14, 15sheathed in the skirt portions 13 d of the plug 13 are inserted in thetwo insertion holes 23, 24, respectively. It should be noted here thatit is preferable that the two insertion holes 23, 24 have a certainlevel of small area within the range of allowing the electrode pins 14,15 to be inserted therein. Specifically, it is preferable that thecross-section area of the insertion hole 23, 24 is more than once to tentimes or less, or preferably in the range of twice to seven times, across-section area of the electrode pin 14, 15 extending through theinsertion hole 23, 24. This construction of the holder 5 can provide theresult that the bottom end face of the plug 13 is abutted with andreceived by a furthest end of the accommodating opening 22 of the holder5. Further, since the insertion holes 23, 24 for the electrode pins 14,15 to extend through them are reduced in area, as compared with those ofthe conventional igniter device 4, the electrode pins 14, 15 areprevented from being burst forth from the holder 5. Also, although theelectrode pins 14, 15 are inserted in the insertion holes 23, 24 to beclosely-spaced from the holder 5, since the plug 13 is provided with theskirt portions 13 d, when static electricity flows in the electric test,the static electricity can be escaped from the space between part of theelectrode pins 14, 15 around which neither the gunpowder nor theenhancer is arranged and the insertion holes 23, 24 of the holder 5, toprevent the electric discharge that may cause the firing of thegunpowder and the enhance.

The holder 5 may be formed of metals such as, for example, aluminum,iron, and stainless steel. Preferably, the holder 5 is formed ofaluminum in terms of easiness for molding, because the holder 5 isrequired to form the insertion holes 23, 24, the accommodating openings21, 22, and the like therein.

The gas generant 2 is packed in the second cup case 3 in the state ofbeing in direct contact with the inner periphery of the second cup case3, without any intermediary of filter and/or coolant. The gas generantsthat may preferably be used include a gas generant comprising anitorogen-containing organic compound as a fuel component, an inorganiccompound as an oxidizing agent component, and at least one additive.Specifically, the fuel components that may be used include at least onematerial selected from the group consisting of aminotetrazole, guanidinenitrate, and nitroguanidine. The oxidizing agent components that may beused include at least one material selected from the group consisting ofstrontium nitrate, ammonium nitrate, potassium nitrate, ammoniumperchlorate, and potassium perchlorate. The additives that may be usedinclude molybdenum trioxide which is an autoignition catalyst. Inaddition to these, a binder and the like can also be cited as theadditive to be added to the gas generant. The binders that may be usedinclude at least one material selected from the group consisting of guargum, methyl cellulose, carboxymethyl cellulose, water-soluble celluloseether, and polyethylene glycol. Gas generant comprising 5-aminotetrazoleand guanidine nitrate as the fuel component, strontium nitrate andammonium perchlorate as the oxidizing agent component, molybdenumtrioxide as the autoignition catalyst, and guar gum as the binder can becited as a preferable gas generant. Further, gas generant comprising10-30 mass % 5-aminotetrazole and 15-35 masst % guanidine nitrate as thefuel component, 10-35 mass % strontium nitrate and 15-35 masst %ammonium perchlorate as the oxidizing agent component, 1-10 masst %molybdenum trioxide as the autoignition catalyst, and 1-10 mass % guargum can be cited as a further preferable gas generant. The gas generantused in the present invention may be molded, for example, in a desirableshape to be packed in the seatbelt pretensioner and the like. Noparticular limitation is imposed on the shape of the molded gasgenerant. The gas generant may be molded in a columnar shape or apellet-like shape. Specifically, after water or an organic solvent isadded to the gas generator in accordance with types of (a) 0.25%-5%cationic binder, (b) 0.25%-5% anionic binder, (c) a fuel, (d) anoxidizing agent, (e) a fuel adjusting agent, and the like, the mixtureis mixed uniformly and kneaded. Then, the resultant mixture is moldedinto columnar molded products by the extrusion molding process and thecutting process or is formed into pellets by using a tableting machineand the like.

The second cup 3 includes a large-diameter cylindrical portion 3 a and aclosed-end cylindrical portion 3 b having two planate side surfaceswhich are continuous to the right side of the cylindrical portion 3 aand parallel with each other. As shown in FIG. 3, six notches 3 c areformed in the bottom of the closed-end cylindrical portion 3 b to extendradially from the center. When the gas generant 2 packed in the secondcup 3 is burnt to thereby generate a high-temperature and high-pressuregas, the notches 3 c are burst open by the pressure of the generated gasand then the gas is discharged directly to the seatbelt pretensioner notshown. The second cup 3 has the flange portion 3 d formed at an endportion thereof on the opening side (the bottom side as viewed in FIG.2) for the fixture to the holder 5, as mentioned later. The materialsthat may be used for forming the second cup 3 include metals, such as,for example, stainless steel, iron, and aluminum.

Now, operation of the gas generator 1 mentioned above will be described.When automobile collision is detected by a collision sensor, not shown,the electric current passes through the two electrode pins 14, 15. Then,the resistance heating element 16 connected to the electrode pins 14, 15generates heat and thereby the firing agent 17 is ignited. Sequentially,the ignition of the firing agent 17 causes the ignition and burning ofthe enhancer agent 10. As the burning of the enhancer agent 10 proceeds,the interior of the first cup 11 of the igniter device 4 is put in thehigh-temperature and high-pressure state. According to the presentinvention, since the first cup 11 is sheathed with and reinforced by theigniter case 12, as shown in FIG. 2, the first cup 11 is prevented frombeing expanded and burst before the enhancer agent 10 is fully burnt.Also, since the two electrode pins 14, 15 are inserted in the two smallinsertion holes 23, 24 formed in the holder 5, respectively, the twoelectrode pins 14, 15 are resistant to being burst forth from the holder5 even in the high temperature and high pressure state of the first cup11.

When the burning of the enhancer agent 10 proceeds, causing the firstcup 11 to rise up to a high temperature and a predetermined highpressure, the high-temperature and high-pressure flame of the enhanceragent 10 is spouted to the gas generant 2 in the second cup 3 at astroke through the flame leading portion 11 a and the flame leadingholes 12 a to ignite the gas generant 2. At this time, the igniter case12, which is fixed to the holder 5 by crimping, is prevented from beingburst forth toward the gas generant 2.

Sequentially, the gas generant 2 is burnt and thereby the pressure ofthe second cup 3 rises up sharply by the gas generated instantaneouslyin the second cup 3 to cause the notches 3 c formed in the second cup 3to burst. Then, the high-temperature and high-pressure gas is introduceddirectly to the seatbelt pretensioner, not shown, to bring the seatbeltpretensioner into operation.

According to the igniter device 4 of this embodiment thus constructed,since the plug 13 is formed of thermosetting resin, the plug 13 isresistant to softening in the high temperature state, so that anincreased strength is provided for the plug 13 under high temperature.Also, since the plug 13 is resistant to softening in the hightemperature state, the electrode pins 14, 15 are prevented from beingdropped out from the plug 13. Also, even when the plug 13 is reduced inthickness, since the strength required for preventing the electrode pins14, 15 from being burst forth can be ensured, the igniter device 4 canbe reduced in size to the extent corresponding to the reduction inthickness of the plug 13. Or, the second cup 3 can be increased involume, thus allowing an increased amount of gas generant 2 packed.Further, since the igniter device is formed of the epoxy resincomposition having good adhesiveness to the metal, the infiltration ofmoisture into the first cup 11 from between the electrode pins 14, 15and the plug 13 can be prevented, thus providing excellent moistureresistance. In addition, since the electrode pins 14, 15 are integrallymolded using the epoxy resin composition, an improved seal can beprovided between the plug 13 and the electrode pins 14, 15 without anyneed of their supporting members. Besides, the parts count of theigniter device 4 can be reduced.

It is particularly preferable that epoxy resin composition is used asthe thermosetting resin composition. This is because since the epoxyresin composition, which comprises the epoxy resin having a high glasstransition point and the curing agent, has good adhesiveness to metal,when the plug 13 is assembled in the gas generator 1, improved adhesionbetween the plug 13 and the electrode pins 14, 15 can be provided tosurely protect the cup packed with the gas generant against infiltrationof moisture into the cup.

Further, the plug 13 is formed to have, at an end portion thereof on theholder 5 side, the stepped portion 13 e to provide a decreased diameterfor the end portion thereof on the holder 5 side. Since the plug 13 has,at its portion on the holder 5 side, the decreased diameter formed bythe stepped portion 13 e, the holder 5 can be formed to have a largerthickness by that extent at its engaging portion to be engaged with thelarge-diameter portion 13 b of the plug 13 than at its engaging portionto be engaged with the small-diameter portion 13 c of the plug 13. Thiscan ensure that the strength of the holder 5 is kept in thehigh-temperature and high-pressure state when the gas generant 2 isburnt.

According to the gas generator 1 of this embodiment thus constructed,the two electrode pins 14, 15 are inserted in the two small insertionholes 23, 24 formed in the holder 5, respectively. Due to this, evenwhen the enhancer agent 10 is burnt to put the second cup 3 in ahigh-temperature and high-pressure state, since a greater part of theend face of the plug 13 b is abutted with and surely received by theholder 5, the two electrode pins 14, 15 are resistant to being burstforth from the holder 5. In addition, since the electrode pins 14, 15are inserted in the insertion holes 23, 24 to be closely spaced from theholder 5, when static electricity flows in the electric test, the staticelectricity is discharged and escaped from the space between part of theelectrode pins 14, 15 around which neither the gunpowder nor theenhancer is arranged and the insertion holes 23, 24 of the holder, toprevent the electric discharge that may cause the firing of thegunpowder and the enhancer agent.

The root portions of the electrode pins 14, 15 extending from the plug13 are sheathed in the skirt portions 13 d, 13 g integrally formed withthe plug 13, and the skirt portions 13 d, 13 g are inserted in theinsertion holes 23, 24, respectively. By virtue of this, when theelectrode pins 14, 15 are inserted in the insertion holes 23, 24,respectively, the fit between the skirt portions 13 d, 13 g and theirrespective insertion holes 23, 24 can be insured to minimize rattle ofthe plug 13 and also provide electrical insulation between the electrodepins 14, 15 and the holder 5 reliably.

Also, the cross-section area of the insertion hole 23, 24 is more thanonce to ten times or less the cross-section area of the electrode pin14, 15, This can provide the results that even when the holder 5 isformed of metal, the short circuit in the electrode pins 14, 15 can beprevented and that even when the resin plug forming the squib issoftened at the ignition in the high temperature state, the electrodepins 14, 15 are prevented from being burst forth from the holder 5

Further, since the sealing material to seal the space between the holder5 and the plug 13 is arranged near the stepped portion 13 e, the secondcup 3 in which the enhancer agent 10 is shielded can be reliablyprotected against infiltration of moisture into it from the spacebetween the holder 5 and the plug 13. Further, it is preferable that aholder portion is formed of metal and also the holder portion and theplug 13 are integrally molded from the epoxy resin composition, becausethis construction can provide so good adhesion between the metal portionand the resin portion that the need of the sealing material can beeliminated.

Although the embodiment wherein the holder 5 and the plug 13 having theelectrode pins 14, 15 are formed separately from each other has beenillustrated above, the holder 5 and the electrode pins 14, 15 may beintegrally molded from the epoxy resin composition. In this variant, theparts count can be reduced and thereby the manufacturing costs can bereduced.

EXAMPLES

The present invention is explained below concretely with reference toExamples but is not limited to these Examples.

Example of Igniter Device Used in the Present Invention Example 1

The plug of the igniter device according to the present invention wasmolded by a so-called cast molding process. Specifically, after epoxyresin composition {(bis-phenol A type epoxy resin and a curing agent(4-methylhexahydrophthalic anhydride): Trade Name; KAYATORON ML-6650Navailable from Nippon Kayaku Co., Ltd.} was mixed, the mixture waspoured into a mold and then cured. The plug was provided with metalpins. Before the plug was molded, the mold was drizzled with a moldrelease agent, first, and, then, the metal pins were put in the mold.Then, the resin composition was prepared. In this preparation process,the epoxy resin was previously heated to about 80° C. and the curingagent was previously heated to about 60° C. Then, after the epoxy resinand the curing agent were weighed and mixed in the proportion of100:100, they were fully agitated. During the agitation, a large amountof air bubbles were produced in the epoxy resin composition of liquidform produced by mixing the bis-phenol A type epoxy resin and the curingagent. Due to this, the mixture was defoamed at 70-80° C. for about10-15 minutes by using a vacuum defoaming machine, during which the moldin which the metal pins were put in place was preheated. Aftercompletion of the defoaming process, the epoxy resin composition inliquid form was transferred into a syringe and then injected in the moldusing a dispenser, while it was warmed to about 50° C. by using aheater. After injected in the mold, the epoxy resin composition wasdefoamed again. Then, it was put in a high temperature oven of 100° C.for three hours and then put in the high temperature oven of 140° C. forthree hours, to be cured. After the epoxy resin composition was cured,the mold was taken out from the high temperature oven and then themolded plug was taken out from the mold. Then, burrs were eliminatedfrom the molded plug, if any. The plug was produced in the mannermentioned above. Then, after a resistance welding of the resistanceheating element and a molding of the firing agent were performed inaccordance with test requirements, the cup packed with the enhanceragent was set in place. The igniter device used in the present inventionwas completed in the manner mentioned above.

Example of Gas Generator of the Present Invention Example 2

The igniter case was assembled in the plug of the igniter deviceproduced in Example 1 and then this assembly was assembled in thealuminum holder to which sealing material had been applied. Then, aftersmokeless gunpowder (gas generant) was packed in the second cup, thesecond cup was fixed by crimping to the holder building the igniterdevice therein.

A flammability test, a pressure proof test, and a humidity test wereperformed using the gas generator of the present invention, to confirmthe effects of the gas generator of the present invention. The gasgenerator of the present invention having the plug of the igniter deviceformed of the epoxy resin composition was used in those tests. On theother hand, for comparison purposes, the gas generator shown in FIG. 6having the plug of the igniter device shown in FIG. 5 formed of PBTresin (polybutylene terephthalate) and the one formed of unsaturatedpolyester were prepared for those tests. The components of the gasgenerant used in the tests comprised nitroguanidine, ammoniumperchlorate, strontium nitrate, binder, and kaolin.

Flammability Test

Test Example 1

First, reference is made to the flammability test. In this test, acylindrical jig having in a bottom thereof a gas discharge hole of 1 mmin diameter and having an inner volume of about 10 cc, and a propaneburner used for heating the jig were used. The gas generator wasinserted in the interior of the jig. In the flammability test, the jigwas set on a base, and the propane burner was set directly below it. Thedistance between a tip end of a nozzle of the propane burner and abottom of the jig was set to be 400 mm and the height of the flame fromthe propane burner was set to be 600 mm by eye. The flammability testwas carried out after the heating was started using the propane burneruntil the gas generant was ignited to thereby generate gases. In thistest, the ignition was confirmed from an explosion one heard.Specifications of the gas generators used for this flammability test andthe results are shown in TABLE 1 below. TABLE 1 Amount of smokelessMaterial of plug of gunpowder (mg) igniter device Results 1,000 Epoxyresin composition Resin member was not broken 1,100 Epoxy resincomposition Resin member was not broken 1,200 Epoxy resin compositionResin member was not broken 1,000 PBT resin composition Resin member wasnot broken 1,100 PBT resin composition Resin member was broken 1,200 PBTresin composition Resin member was broken 1,000 Unsaturated polyesterResin member was not broken 1,100 Unsaturated polyester Resin member wasnot broken 1,200 Unsaturated polyester Resin member was not broken

It can be seen from TABLE 1 that in the gas generator incorporatingtherein the igniter device having the plug formed of PBT resin, when anamount of smokeless gunpowder used was 1,000 mg, the PBT resin memberwas not broken, but when the amount of smokeless gunpowder used were1,100 mg and 1,200 mg, the PBT resin member was broken. In the gasgenerator incorporating therein the igniter device having the plugformed of unsaturated polyester, when the amount of smokeless gunpowderused were 1,000 mg, 1,100 mg, and 1,200 mg, the unsaturated polyesterresin member was not broken. On the other hand, in the gas generatorincorporating therein the igniter device having the plug formed of epoxyresin composition, when the amount of smokeless gunpowder used were1,000 mg, 1,100 mg, and 1,200 mg, the epoxy resin member was not broken.It were found from these that the gas generator of the present inventionincorporating the igniter device having the plug formed of the epoxyresin composition or the unsaturated polyester has an advantage instrength in the high temperature state over the gas generatorincorporating the igniter device having the plug formed of the PBTresin.

Pressure Proof Test

Example 2

Second, reference is made to the pressure proof test. In this test,three different types of gas generators were prepared. One was a gasgenerator wherein an igniter device having a plug formed of the commonlyused PBT resin was assembled in a holder and a cup was fixed thereto bycrimping. Another one was a gas generator wherein the plug of theigniter device of the present invention was molded and assembled in anigniter case as described above, the resulting assembly was assembled inan aluminum holder to which sealing material was applied, and a cupmember was fixed thereto by crimping. Still another one was a gasgenerator wherein an igniter device having a plug formed of unsaturatedpolyester was assembled in the holder and then a cup member was fixedthereto by crimping. The gas generant was not packed in any of these gasgenerators. These gas generators were subjected to the pressure prooftest. In the pressure proof test, each of these gas generators was seton a jig having an inner volume of 3.5 cc, first. Then, after the jig isfilled with oil, hydraulic pressure was put on the gas generatorgradually until the gas generator was broken, and the pressure at whichthe gas generator was burst was measured. The results obtained in thispressure proof test are shown in TABLE 2. TABLE 2 Material of plug ofLength of plug Measured pressure Occurrence igniter device (mm) value(MPa) of burst PBT resin 3.6 150 Burst composition Epoxy resin 2.9 189Not burst composition Unsaturated 2.9 185 Not burst polyester

As seen from TABLE 2, in the conventional gas generator incorporatingtherein the igniter device having the plug formed of the PBT resin, theresin member was burst at 150 MPa. In contrast to this, the gasgenerator of the present invention incorporating therein the igniterdevice having the plug formed of the epoxy resin composition, the resinmember was not burst although the pressure put thereon rose up to 189MPa. Also, the gas generator of the present invention incorporatingtherein the igniter device having the plug formed of the unsaturatedpolyester, the resin member was not burst although the pressure putthereon rose up to 185 MPa. In addition, although the gas generator ofthe present invention incorporating therein the igniter device havingthe plug formed of the epoxy resin composition or unsaturated polyesterand having a length of 2.9 mm was shorter in length of the resin memberby 0.7 mm than the conventional gas generator incorporating therein theigniter device having the plug formed of the PBT resin and having alength of 3.6 mm, the results were that the gas generator of the presentinvention had an advantage in strength over the conventional gasgenerator.

Humidity Test

Example 3

Further, reference is made to the humidity test. In this test, threedifferent types of gas generators were prepared. One was a gas generatorwherein an igniter device having a plug formed of the commonly used PBTresin was assembled in a holder through an O-ring and a cup was filledwith gas generant and fixed to the holder by crimping. Another one was agas generator of the present invention wherein the holder and theelectrode pins were integrally molded using the epoxy resin compositionand a cup was filled with gas generant and fixed to the holder bycrimping. Still another one was a gas generator wherein the holder andthe electrode pins were integrally molded using the unsaturatedpolyester and a cup was filled with gas generant and fixed to the holderby crimping. An amount of gas generant packed was Ig. These three gasgenerators were subjected to the humidity test. The test conditions wereso set that temperature was 85° C., humidity was 85%, and test time was410 hours. After a sample was taken out from an environmental testmachine, the gas generant was taken out from the gas generator, so thatthe moisture absorption amount was measured. The test results in thistest are shown in TABLE 3. TABLE 3 Specification of gas generatorMoisture absorption amount (%) Sealing structure using O-ring 0.41(Conventional) Sealing structure using adhesion of 0.16 epoxy resinSealing structure using adhesion of 0.53 unsaturated polyester

As seen from TABLE 3, in the conventional sealing structure using anO-ring, when measured under the atmosphere of temperature of 85° C. andhumidity of 85% for 410 hours, the amount of moisture absorption of thegas generant was 0.41%. In contrast, in the sealing structure of thepresent invention using the adhesion of epoxy resin, the amount ofmoisture absorption of the gas generant was 0.16% and in the sealingstructure of the present invention using the adhesion of unsaturatedpolyester, the amount of moisture absorption of the gas generant was0.53%. It was found from these that the moisture absorption resistanceof the gas generator of the present invention having the sealingstructure wherein the holder and the electrode pins were allowed toadhere to each other using the epoxy resin composition was 2.6 times ormore as high as that of the conventional gas generator having thesealing structure using the O-ring. It was also found that the moistureabsorption resistance of the gas generator of the present inventionhaving the sealing structure wherein the holder and the electrode pinswere allowed to adhere to each other using the epoxy resin compositionwas 3.3 times or more as high as that of the gas generator of thepresent invention having the sealing structure wherein the holder andthe electrode pins were allowed to adhere to each other using the epoxyresin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an igniter device used in the presentinvention, taken along line III-III of FIG. 2;

FIG. 2 is a sectional view of a gas generator according to an embodimentof the present invention;

FIG. 3 is a view of a bottom portion of a second cup of the gasgenerator of FIG. 2;

FIG. 4 is a sectional view taken along line VI-VI of FIG. 2;

FIG. 5 is a sectional view of a conventional igniter device; and

FIG. 6 is a sectional view of a conventional gas generator.

EXPLANATIONS OF LETTERS AND NUMERALS

-   1 Gas generator-   2 Gas generant-   3 Second cup-   3 a Cylindrical portion-   3 b Closed-end cylindrical portion-   3 c Notch-   3 d Flange portion-   4 Igniter device-   5 Holder-   5 a Projection-   5 b Accommodating portion-   5 c Annular projection-   10 Enhancer agent-   11 First cup-   11 a Flame leading portion-   11 b Engaging portion-   12 Igniter case-   12 a Flame leading hole-   12 b Flange portion-   13 Plug-   13 b Large diameter portion-   13 c Small diameter portion-   13 a Insertion portion-   13 e Stepped portion-   13 d Skirt portion-   13 f Intermediate portion-   14 Electrode pin-   15 Electrode pin-   16 Resistance heating element-   17 Firing agent-   18 Gasket-   19 Shorting clip-   21 Accommodating opening-   22 Accommodating opening-   23 Insertion hole-   24 Insertion hole

1. An igniter device comprising a resistance heating element, gunpowderto be ignited by heat generation of the resistance heating element,electrode pins connected to the resistance heating element, and a plugfor holding the electrode pins, and sealing a contact interface betweenthe electrode pins and the plug, wherein material of the plug is anepoxy resin composition.
 2. The igniter device according to claim 1,wherein the epoxy resin composition comprises an epoxy resin and acuring agent.
 3. The igniter device according to claim 1, wherein theepoxy resin composition comprises 30-95 weight % filler of the totalepoxy resin composition.
 4. The igniter device according to claim 3,wherein the filler comprises at least one material selected from thegroup consisting of molten silica, crystallized silica, aluminum oxide,calcium carbonate, and mixtures thereof.
 5. The igniter device accordingto claim 1, wherein the epoxy resin composition comprises at least oneresin selected from the group consisting of bisphenol type epoxy resin,novolak type epoxy resin, biphenyl type epoxy resin, naphthalene typeepoxy resin, alicyclic epoxy resin, amines epoxy resin, and combinationsthereof.
 6. The igniter device according to claim 2, wherein the curingagent comprises at least one material selected from the group consistingof phenol novolak resin, acid an hydride, amines, and combinationsthereof.
 7. The igniter device according to claim 2, wherein the epoxyresin composition further comprises a curing accelerator.
 8. The igniterdevice according to claim 1, wherein the plug comprises, at a portionthereof on the electrode pin side, a small diameter stepped portion.9-10. (canceled)
 11. A gas generator comprising a cup packed with gasgenerant to generate gas by burning, an igniter device arranged in aninterior of the cup, and a holder for holding the igniter device and thecup, the igniter device comprising a resistance heating element,gunpowder to be ignited by heat generation of the resistance heatingelement, electrode pins connected to the resistance heating element, anda plug for holding the electrode pins, wherein material of the plug isan epoxy resin composition, and wherein the holder has insertion holesfor allowing the electrode pins to extend through them, respectively.12. The gas generator according to claim 11, wherein root portions ofthe electrode pins extending from the plug are sheathed with skirtportions formed to be integral with the plug and the skirt portions areinserted in the insertion holes.
 13. The gas generator according toclaim 11, wherein the plug has, at a portion thereof on the electrodepin side, a small diameter stepped portion. 14-15. (canceled)
 16. Thegas generator according to claim 11, wherein the epoxy resin compositioncomprises an epoxy resin and a curing agent.
 17. The gas generatoraccording to claim 11, wherein the epoxy resin composition comprises30-95 weight % filler of the total epoxy resin composition.
 18. The gasgenerator according to claim 11, wherein the filler comprises at leastone material selected from the group consisting of molten silica,crystallized silica, aluminum oxide, calcium carbonate, and combinationsthereof. 19-23. (canceled)
 24. The gas generator of claim 11, whereinthe epoxy resin comprises at least one resin selected from the groupconsisting of bisphenol type epoxy resin, novolak type epoxy resin,biphenyl type epoxy resin, naphthalene type epoxy resin, alicyclic epoxyresin, amines epoxy resin, and combinations thereof.
 25. The gasgenerator of claim 16, wherein the curing agent comprises at least onematerial selected from the group consisting of phenol novolak resin,acid anhydride, amines, and combinations thereof.
 26. The gas generatorof claim 11, wherein the epoxy resin composition further comprises acuring accelerator.
 27. The gas generator of claim 11, wherein across-section area of the insertion hole ranges from more than one toten times a cross-section area of the electrode pin.
 28. The gasgenerator of claim 13, further comprising a sealing material, arrangednear the stepped portion, for sealing a space between the holder and theplug.